The biochemical mechanisms by which aldosterone and vasopressin regulate the movement of sodium and water through epithelium membranes (kidney and toad bladder) will be studied. The characteristics of the specific binding of aldosterone by epithelial cells will be studied and the specific protein receptors for the steroid isolated and characterized. The binding of the receptor-protein-steroid complex by nuclei from toad bladder and kidney will be studied and the RNA consequently synthesized will be isolated and its physical properties measured. We will continue our purification of the aldosterone-induced protein(s) from toad bladder mucosal cells. Parallel attempts to isolate the steroid-induced proteins from the kidney are being pursued. One of the major goals will be determining whether the induced proteins are identical. The induced proteins will be studied for possible binding and catalytic properties in an attempt to determine their role in the expression of the mineralocorticoids' effects upon transport. We will also be studying the vasopressin-stimulated adenylate cyclase to determine whether any of those aldosterone-induced proteins enhance the activity of this enzyme. The proteins will also be assayed for effects upon cAMP-stimulated protein kinase activity.